1. Technical Field
This invention generally relates to a method of preparing and preserving fresh, refrigerated mashed potatoes in sealed containers, and more particularly to a method or process of preparing fresh mashed potatoes for storage in sealed containers for extended periods of time under refrigerated conditions.
2. Background Art
Since the introduction of the potato to western civilization in the mid 1500's, the traditional method of preparing potatoes for human consumption has been for the consumer to purchase them as fresh, unpeeled produce, which are then washed, peeled, cut and cooked for consumption. This process tales anywhere from 30 to 60 minutes and has always been considered a rather time consuming chore. As a result, commercially prepared potato products are immensely popular with the consuming public, since these time consuming tasks are performed at a processing plant, thus saving the consumer considerable time and effort. This has resulted in explosive growth in the frozen potato product industry. However, while frozen potato products are easily preserved for extended periods of time, they are generally considered to be of inferior quality and taste when compared to fresh, refrigerated potato products.
The problem has been, and always will be, that the atmosphere in which we live is highly contaminated with microbial organisms, such as yeast and bacteria. These microorganisms thrive in the atmosphere at ambient temperatures, and to a lesser degree, at refrigerated temperatures in the 32.degree. F. to 38.degree. F. range. This is not a significant problem for frozen potato products, since at the lower freezing temperatures growth of microbial organisms is effectively inhibited.
With fresh, refrigerated potato products, there have been two basic methods of reducing spoilage during extended refrigerated storage, these have been: first, to eliminate or drastically reduce the number of organisms present with the food product before storage; second, to eliminate the atmospheric conditions which permit growth.
One past method to reduce the number of organisms present has been the addition of additives, most commonly sodium bisulfite, as a source of sulfur dioxide to retard nonenzymatic browning. A second method to reduce the number of organisms present has been the addition of monoglyceride emulsifier, which functions as an anti oxidant, and sodium acid pyrophosphate, which reacts with trace amounts of iron to prevent after-cooking discoloration. However, the federal government and many states have enacted legislation or established regulations which drastically limit the permissive use of these additives, and as a result their effectiveness will be more limited.
Blanching or raising the temperature of the vegetable product, has been found to reduce microorganisms found on the surface of whole or cut potato products.
The second solution is to eliminate the atmospheric conditions under which these organisms can grow and multiply. It has been known for a long time that preserving refrigerated food products in an inert atmosphere within an hermetically sealed container extends refrigeration shelf life for fresh food products. Such a method of preserving food products is disclosed in U.S. Pat. No. 1,821,106.
It is also known that it is possible to extend the refrigerated shelf life by depositing precooked potato pieces, from which micro organisms have been eliminated by the process of cooking, into packaging containers which have been flushed with mixtures of nitrogen and carbon dioxide, and sealed. Such a method is disclosed in Ruggerone, U.S. Pat. No. 3,773,527. And, cooking potatoes within the packaging to provide for an expulsion of the air within the package, as the product cools within the sealed packages, is disclosed in Mohwinkel, U.S. Pat. No. 4,135,003.
To date, reasonable success has been achieved in processing for extended refrigerated shelf life whole and cut potato pieces. The reason for this is that these products are particulate solids and successful effort has been directed toward the surface environments of the products with little attention directed toward the interior product cores which are presumably wholesome and not significantly at risk for contamination with microbial organisms.
Mashed potatoes, on the other hand, present an entirely different and unique set of problems. It has been known for years that in order to produce mashed potatoes, the potatoes must first be cooked, preferably at boiling water temperature, for approximately 30 to 35 minutes. The conventional teachings are quite clear that the potatoes should, under no circumstances be overcooked because overcooking will result in the release of free starch which will retrograde, upon cooling, to a sticky gel, which in turn will result in pasty or sticky mashed potatoes that are too viscous to commercially process easily and of an unacceptable texture, or mouth feel, for wide acceptance by the consuming public.
Again, using the conventional process, after the potatoes have been cooked, but not overcooked, the potatoes are then ground to break up the multicellular structure of the potatoes without breaking the individual cells apart, then mixed with either fresh milk or reconstituted milk, salt, and some sort of a fat, either butter or margarine, for flavoring. This addition of flavorings and moisturizers gives rise to another problem which is contaminated entrained air being present within the mashed potatoes. Removal of the entrained air is very difficult, if not impossible, and as a result commercially produced mashed potatoes, to date, have always suffered from an unacceptably short refrigerated shelf life.
Accordingly, it is an object of this invention to provide a process for preparing fresh mashed potatoes which have an extended refrigerated shelf life in the range of 6 to 8 weeks. The second object of this invention is to provide a process for producing fresh, refrigerated mashed potatoes of a pleasing texture, quality and color for an extended shelf life. A third object is to reduce the viscosity of the mashed potatoes and mashed potato mixture to the point that it is possible to pump them in a closed system during processing so that entrainment of air is minimized and pasteurization and refrigeration are feasible to reduce microbial contamination and extend shelf life. A fourth object is reduce the sticky or pasty texture at the time of consumption which is so prevalent in commercially processed mashed potatoes today.